1. Field of the Invention
The present invention relates to an authentication method, an authentication apparatus, an authentication system and an IC card.
2. Description of the Background Art
In order to enable only registered users to use services provided by a common carrier, a procedure of authentication is necessary for determining whether or not the users are registered. In general authentication utilizing a semiconductor element with an IC card or the like, for example, the semiconductor element formed as a nonvolatile memory preserves a number serving as an authentication signal for determining whether or not the user using the IC card or the like is registered on the basis of whether or not the number coincides with a registered number.
In such conventional authentication, however, it is necessary to form the nonvolatile memory for preserving the authentication signal in a semiconductor integrated circuit in the first place, and to write the authentication signal in the nonvolatile memory in the second place.
According to a first aspect of the present invention, an authentication method comprises steps of (a) obtaining an authentication signal on the basis of electric noise of a semiconductor element and (b) comparing the authentication signal obtained in the step (a) with each of at least one registered authentication signal and determining coincidence in any comparison.
In the authentication method according to the first aspect, the electric noise of the semiconductor element is specific to each element and hence the authentication signal obtained on the basis thereof is also specific to each element. Therefore, it is not necessary to form a nonvolatile memory or write the authentication signal for implementing authentication but the semiconductor element may simply be manufactured through the same manufacturing steps. Thus, authentication can be simply performed at a low cost.
According to a second aspect of the present invention, the authentication method further comprises a step of (c) recording the authentication signal as one of at least one registered authentication signal.
In the authentication method according to the second aspect, a semiconductor element for which an authentication signal has already been obtained can be distinguished from other ones to be authenticated.
According to a third aspect of the present invention, the step (b) comprises steps of (b-1) determining whether or not at least one registered authentication signal is present and (b-2) comparing each of at least one registered authentication signal with the authentication signal and determining coincidence in any comparison when a positive determination is obtained in the step (b-1), and wherein the authentication signal is recorded as one of at least one registered authentication signal in the step (c) only when a negative determination is obtained in the step (b-1) or a negative determination is obtained in the step (b-2).
In the authentication method according to the third aspect, an authentication signal intended to be newly registered is registered only when there is no registered authentication signal coinciding with the authentication signal, whereby double registration can be prevented.
According to a fourth aspect of the present invention, the step (a) includes a step (a-1) of measuring the electric noise with respect to the semiconductor element thereby obtaining a code or codes depending on the frequency spectrum of the electric noise as the authentication signal.
In the authentication method according to the fourth aspect, a code varying with each semiconductor element while reflecting noise specific to the semiconductor element is obtained as the authentication signal.
According to a fifth aspect of the present invention, the semiconductor element comprises a plurality of unit semiconductor elements, and the step (a-1) comprises a step (a-1-1) of measuring electric noise with respect to the respective ones of the plurality of unit semiconductor elements thereby obtaining codes depending on the frequency spectra of the electric noise and regarding a set of the codes as the authentication signal.
In the authentication method according to the fifth aspect, the codes depending on the frequency spectra of the plurality of unit semiconductor elements are obtained as the authentication signal, whereby it is possible to reduce such a possibility that the same authentication signal is obtained although the semiconductor elements are different from each other. Thus, the range of users requiring authentication can be further enlarged.
According to a sixth aspect of the present invention, a set of numerical values expressing the values of the frequency spectra corresponding to a plurality of frequencies are obtained as the codes in the step (a).
In the authentication method according to the sixth aspect, the set of the numerical values expressing the values of the frequency spectra corresponding to the plurality of frequencies are obtained as the authentication signal, whereby the authentication signal can be generated by employing a simple circuit.
According to a seventh aspect of the present invention, the semiconductor element has at least one MOSFET.
In the authentication method according to the seventh aspect, the semiconductor element employed as the object of extraction of the authentication signal has the MOSFET, whereby an authentication signal remarkably varying with each semiconductor element can be obtained.
According to an eight aspect of the present invention, an authentication apparatus comprises an authentication signal extraction part generating and outputting an authentication signal with respect to a detachably connected semiconductor element on the basis of its electric noise, a storage part storing at least one registered authentication signal each comparable with the authentication signal, a comparison part comparing the authentication signal output from the authentication signal extraction part with at least one registered authentication signal stored in the storage part, and a control part making the comparison part compare the authentication signal output from the authentication signal extraction part with each of at least one registered authentication signal stored in the storage part for executing authentication processing determining coincidence in any comparison.
In the authentication apparatus according to the eighth aspect, the electric noise of the semiconductor element is specific to each element, and hence the authentication signal obtained on the basis thereof is also specific to each element. Therefore, it is not necessary to form a nonvolatile memory or write the authentication signal for implementing authentication but the semiconductor element may simply be manufactured through the same manufacturing steps. Thus, authentication can be simply performed at a low cost.
According to a ninth aspect of the present invention, the control part selectively executes the authentication processing and registration processing making the storage part store the authentication signal output from the authentication signal extraction part as one of at least one registered authentication signal.
In the authentication apparatus according to the ninth aspect, a semiconductor element for which an authentication signal has been obtained can be distinguished from other ones to be authenticated.
According to a tenth aspect of the present invention, the control part selectively executes the authentication processing and registration processing making the comparison part compare the authentication signal output from the authentication signal extraction part with each of at least one registered authentication signal stored in the storage part for making the storage part store the authentication signal only when no coincidence is recognized in any comparison.
In the authentication apparatus according to the tenth aspect, an authentication signal intended to be newly registered is registered only when there is no registered authentication signal coinciding with the authentication signal, whereby double registration can be prevented.
According to an eleventh aspect of the present invention, the authentication signal extraction part measures the electric noise with respect to the semiconductor element thereby generating a code or codes depending on the frequency spectrum of the electric noise and outputting the code or codes as the authentication signal.
In the authentication apparatus according to the eleventh aspect, a code varying with each semiconductor element while reflecting noise specific to the semiconductor element is obtained as the authentication signal.
According to a twelfth aspect of the present invention, the authentication signal extraction part measures, with respect to an element comprising a plurality of unit semiconductor elements as the semiconductor element, electric noise of the respective ones of the plurality of unit semiconductor elements thereby obtaining codes depending on the frequency spectra of the electric noise and outputting a set of the codes as the authentication signal.
In the authentication apparatus according to the twelfth aspect, the codes depending on the frequency spectra of the plurality of unit semiconductor elements are obtained as the authentication signal, whereby it is possible to reduce such a possibility that the same authentication signal is obtained although the semiconductor elements are different from each other. Thus, the range of users requiring authentication can be further enlarged.
According to a thirteenth aspect of the present invention, the authentication signal extraction part generates a set of numerical values expressing the values of the frequency spectra corresponding to a plurality of frequencies as the codes.
In the authentication apparatus according to the thirteenth aspect, the set of the numerical values expressing the values of the frequency spectra corresponding to the plurality of frequencies are obtained as the authentication signal, whereby the authentication signal extraction part can be formed by a simple circuit.
According to a fourteenth aspect of the present invention, an authentication system comprises a terminal having an authentication signal extraction part generating and outputting an authentication signal with respect to a detachably connected semiconductor element on the basis of its electric noise and common carrier equipment, connected to the terminal through a communication line, having a storage part storing at least one registered authentication signal each comparable with the authentication signal, a comparison part comparing the authentication signal output from the authentication signal extraction part with at least one registered authentication signal stored in the storage part and a control part making the comparison part compare the authentication signal output from the authentication signal extraction part with each of at least one registered authentication signal stored in the storage part for executing authentication processing determining coincidence in any comparison.
In the authentication system according to the fourteenth aspect, the electric noise of the semiconductor element is specific to each element, and hence the authentication signal obtained on the basis thereof is also specific to each element. Therefore, it is not necessary to form a nonvolatile memory or write the authentication signal for implementing authentication but the semiconductor element may simply be manufactured through the same manufacturing steps. Thus, authentication can be simply performed at a low cost. Further, the terminal is connected with the common carrier equipment through the communication line, whereby the user can be authenticated for enjoying services provided by the common carrier at a long distance.
According to a fifteenth aspect of the present invention, an IC card comprises a semiconductor device having an integrated circuit and a semiconductor element built into the same semiconductor substrate and a terminal group including a plurality of terminals connected to the semiconductor element for enabling connection between the semiconductor device and the exterior.
In the IC card according to the fifteenth aspect, the semiconductor element for authentication is built into the same semiconductor substrate along with the integrated circuit, whereby the cost for forming the semiconductor element for authentication can be reduced.
According to a sixteenth aspect of the present invention, the IC card further comprises a switching element interposed between the semiconductor element and at least one of the plurality of terminals, and the terminal group further includes a terminal relaying a signal controlling the switching element.
The IC card according to the sixteenth aspect comprises the switching element which can be controlled through the terminal, whereby the semiconductor element for authentication can be protected against static electricity or the like so that noise characteristics can be stabilized.
According to a seventeenth aspect of the present invention, the semiconductor element has at least one MOSFET.
In the IC card according to the seventeenth aspect, the semiconductor element has the MOSFET, whereby an authentication signal remarkably varying with each semiconductor element can be obtained.
An object of the present invention is to provide an authentication method, an authentication apparatus, an authentication system and an IC card requiring neither formation of a nonvolatile memory nor writing of an authentication signal.